In particular, they've been analyzing which of the genre magazines have published work by "world" SF writers.
There is some debate between the two of them as to what defines a "world" SF writer. Charles opts for a broader definition than Lavie does, but in general they're defining said "world" writers to be those who don't come from the traditional Anglophone world (US, UK, Australia, and English-speaking Canada), nor are they including Anglophone ex-pats living abroad.
There is, however, something fundamental which I think both of them are overlooking, and that is the issue of translation.
Most "world" (using the definition of non-Anglophone) or "international" writers write in a language other than English. As such, the process for their work to reach an English-language audience is even more complicated than the simple submission and acceptance/rejection model which English-language writers face.
In order for these international writers to even have their work considered, one of these scenarios needs to happen:
A) an editor who is able to read the language finds a work she wishes to publish and commissions a translation or translates said work herself;
B) a reader's report by someone who can read the language is commissioned by the editor or the publishing house to evaluate whether or not a decision to buy the book/story will be made;
or C) a translation is made into English, either by the author herself or by a (fan or professional) translator, which is then submitted via the traditional submission->rejection/acceptance channels.
Of these scenarios, C is without a doubt the most common one, for a variety of reasons.
Since most of the SF editors can barely keep up with their own slush piles, it is not common for them to be actively scouring foreign publications for possible work to publish. Aside from the simple fact that many Anglophone editors do not speak any other languages sufficiently well to read and consider such work.
Scenario B is more relevant to book publication than short fiction (what has been under discussion most recently in terms of World SF Writers in the major short fiction markets) and usually occurs when a work has been submitted by a foreign agent. Alternatively, it can be by recommendation from someone whose taste or judgment the editor trusts.
And unfortunately the decision will be weighted not only by the usual concerns in today's tight publishing climate: quality, marketing, etc. which affect English-language writers as well, but additionally by the cost of commissioning a translation. Which, frankly, most publishers (whether of books or short fiction) are not willing to pay for.
Which is why what few works do make it into the submission system usually do so via Scenario C, because this way it is either at the author's own expense (whether translating the work herself or paying out-of-pocket for a translation to be done) or at the translator's own expense (translating the work out of love, as a favor to the author, as an academic project, or on spec in the hopes of being able to place the work and recoup some income from the endeavor at a later date by sharing the fee paid to the author).
Something to be kept in mind when discussing what "world" SF stories have or have not been published, and some of the underlying issues of access and privilege which might account for the situation being as it is.
One thing that would be nice is if the World SF News Blog would highlight translators by name when mentioning those World SF stories that do appear in translation. This would, I think, be in keeping with their mission to bring attention to World SF, and the people who help bring it to English-speaking readers.